Take the Pausing a Thread example. If I use notifyAll instead of notify, is there any side effect, and is it necessary?
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I have implemented a simple profiler with JVMTI to display the invocation on wait() and notifyAll(). As a test case I am using the. producer consumer example of Oracle. ... |
Well, I supposed you've noticed that there's no built-in functionality to support this. One of the primary reasons why Java lacks this support is that it's rarely needed. If you have synchronized code that takes a long time to execute (but which many threads will be accessing), you should reconsider your design to make sure you're doing it the best way. ... |
Perhaps the mother of stupid questions, but here it is: consider an application that that stores data( a vector) by serialisation (on a floppy!). void save(){ synchronized(vector){ //code to do the serialisation } } Object getObject(int i){ synchronised(vector){ return vector.elementAt(i); } } //etc These methods are 'triggered" by different threads. My question: is there any benefit by using wait() and/or notifyAll() ... |
I agree. Try adding another static variable, say a String called "lock". Synchronize on lock and then lock.notifyAll() when you're done. Since it's static, all instances will be synchronizing on the same object. Going at another angle ... if your true objective is to never run more than three of something at a time, look into thread pooling with Executor in ... |
synchronizing and waiting are different things. you dont wait because you cant access a synchronized block of code. You wait for some logical reason, like the bus has not arrived yet or its not 5pm yet. synchronizing and waiting are totally different concepts. Though to wait you will need to use synchronization. |
The code is as follows CubbyHole.java ================ class CubbyHole{ int item;static boolean isItemSet; public synchronized void get(){ if (isItemSet==false){ try{ this.wait();} catch (InterruptedException ie){System.out.println("InterruptedException occured in get() of ubbyHole : "+ie);}} System.out.println(Thread.currentThread().getName()+" Got : "+item);isItemSet = false; notifyAll();} public synchronized void put(int item) {if (isItemSet==true){ try{ this.wait();} catch (InterruptedException ie){ System.out.println("InterruptedException occured in get() of CubbyHole : "+ie);}} this.item = item; ... |
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Hi, notifyAll() definitely has the obvious overhead to go through all threads in the object's wait list vs. just picking one in notify(). It is a O(n) vs. O(1) issue. But I am thinking if people are actually referring to another potentially worse overhead when we say notifyAll() is bad. Typical case: 1: public synchronized int get() { 2: while (available ... |
I have a doubt in notifyAll.I refering K&B.In the notify section i done a program in the text.i had shown the code below public class Reader extends Thread{ Calculator c; public static void main(String[] args) { Calculator calculator=new Calculator(); Reader r1=new Reader(calculator); Reader r2=new Reader(calculator); Reader r3=new Reader(calculator); r1.setName("First"); r2.setName("Second"); r3.setName("Third"); r1.start(); r2.start(); r3.start(); calculator.start(); } public Reader(Calculator c) { this.c=c; ... |
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I wanted to write a program about notifyAll: public class Main { /** Creates a new instance of Main */ public static void main(String[] args) { // TODO code application logic here distanceshow d=new distanceshow(); Thread thread1 = new Thread(d); Thread thread2 = new Thread(d); Thread thread3 = new Thread(d); thread1.start(); thread2.start(); thread3.start(); } } public class distanceshow implements Runnable { ... |
Hi all! I have an object that implements a remote observer pattern. The observer is is exported to the RMI Registry (at JVM1) and is notified by an observable object from another RMI registry (JVM2). In the JVM1 this object, when notified, should invoke notifyAll() so other objects that are waiting but not exported to the JVM1' s registy can continuous ... |
Dear all, In the book of K&B, there is an example about how to use notifyAll() for thread communication. However, in the class Calculator below, if I remove the notifyAll(), the program stills works well. Can anybody tell me why? public class Reader extends Thread { Calculator c; public Reader(Calculator calc) { c = calc; } public void run() { synchronized(c) ... |
class WaitNotifyAllDemo { public static void main (String [] args) { Object lock = new Object (); MyThread mt1 = new MyThread (lock); mt1.setName ("A"); MyThread mt2 = new MyThread (lock); mt2.setName ("B"); MyThread mt3 = new MyThread (lock); mt3.setName ("C"); mt1.start (); mt2.start (); mt3.start (); System.out.println ("main thread sleeping"); try { Thread.sleep (3000); } catch (InterruptedException e) { } ... |
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Totally wrong in every regard 1. wait / notify/ notifyall are defined in object and can be called on any object, provided you have synchronized on that object first. There is no "in a thread / not in a thread" 2. It is a seriously bad idea to be calling notify or notifyall on a Thread object (which you were theoretically ... |
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